The present invention concerns a suction device for a double-point coating system.
In double-point coating, first a paste is applied to a fabric web in dots at even intervals and a powder is then sprinkled over it, by means of which the paste points or bumps and the areas in between them are at least partially covered with the powder.
However, the goal of double-point coating is to produce fabric webs that have, at least on one top side, individual nops or dots made of a paste and a powder sprinkled on them connected to the paste, so that the fabric web stays uncoated in the areas between the individual nops or dots. Therefore, suction devices are used that suck loose powder off the fabric web.
A proven suction device is known in which a fabric web is run under a powder-suction element which sucks off the loose powder. Two suction nozzles are arranged in the direction in which the fabric web moves, before and after the powder-suction element, that suck down the fabric web from underneath and thus provide tension on the fabric web. A beater roller is arranged in the direction of movement in front of the powder-suction element, said beater roller making a beating motion on the bottom of the fabric web, thus throwing the powder up before it is caught by the powder-suction element and sucked off for further use or disposal.
Although this double-point suction device yields satisfactory results, the arrangement of the paste/powder points has nonetheless often been shown to be uneven and, in serious cases, the powder even clogs the fabric. This is especially true in the case of elastic materials. The reason for this is that the fabric webs in the double-point suction device are subjected to tension, which stretches the fabric.
The problem of the present invention is to create a double-point suction device in which the fabric web is subjected to no tension or subjected only to slight tension.